Three-way call detection and response system

ABSTRACT

A three-way call detection and response system comprising, in accordance with a preferred embodiment, a three-way call detector coupled non-intrusively, by a bridge repeater, to a communication path carrying digital signals between originator and recipient end office telecommunication switches. The three-way call detector includes an interface and a digital signal processor electrically connected to the bridge repeater for receipt of digital signals from the communication path. The three-way call detector also includes a local controller which interacts with the interface, a digital signal processor, and a remote controller. The remote controller executes a plurality of software programs which control operation of the system. In accordance with a preferred method, the three-way call detection and response system monitors the communication path for indicia representative of a three-way call signature and, hence, an attempted three-way call placement. Upon identifying a suspected three-way call signature, the system examines the digital signals to determine the spectral characteristics of a suspected release pulse of the suspected three-way call signature. Using pattern recognition techniques to compare the spectral characteristics of the suspected release pulse with the spectral characteristics of known, reference release pulses, the system determines whether or not the release pulse is substantially similar to the release pulse of an actual three-way call signature. If so, and after also identifying first and second periods of silence about the release pulse, the system responds to the detection, for example, by disconnecting the telephone call, playing a recording over the communication path, or creating a record of the attempted three-way call placement.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of telephone callcontrol and, in its most preferred embodiments, to the field ofapparatus and methods for detecting and responding to an attemptedthree-way telephone call placement.

Today's modern telephone systems provide individuals and businesses witha variety of customizable telephone features and services. One of thesefeatures, known as conference or "three-way" calling, enables atelephone customer having three-way calling service (also referred toherein as the telephone call recipient or simply, the recipient) toestablish a telephone connection between a telephone call originator(also referred to herein as the originator), himself (i.e., thetelephone call recipient), and a third party. To establish theconnection or "three-way call", the recipient receives a telephone callfrom the originator and subsequently places the telephone call on holdby depressing and releasing the switch hook on his telephone. Uponreceiving a dial tone, the recipient dials the telephone number of thethird party and establishes a connection with the third party. Then, therecipient depresses and releases his switch hook a second time toconnect all three individuals.

The telephone call recipient generally receives basic telephone serviceand additional services, including three-way calling service, from alocal telephone company having a telephone switch (also referred toherein as the recipient's end office switch) located at an end officenear the location of the recipient's telephone. The recipient's endoffice switch connects to the recipient's telephone via, at least, acodec device (which converts signals between analog and pulse codemodulated (PCM) digital forms) and a distribution network which carriesanalog signals between the codec device and the recipient's telephone.Similarly, the telephone call originator generally receives telephoneservice from a local telephone company having a telephone switch (alsoreferred to herein as the originator's end office switch) located at anend office near the location of the originator's telephone. Therecipient's telephone is similarly connected to the recipient's switchby a codec device and an analog distribution network. When theoriginator places a telephone call to the recipient, the originator'send office switch routes the call to the recipient's end office switchand, hence, to the recipient via, generally, digital T1 facilities whichinclude a number of other telephone switches (including, but not limitedto interchange carrier switches, access tandem switches, and other endoffice switches). Together, the switches, T1 facilities, codecs, andanalog distribution network are referred to by those skilled in the artas the public switched network or PSN. The routing process and T1facilities define two, one-way, digital communication paths between theoriginator's end office switch and the recipient's end office switch.The first communication path carries signals transmitted by theoriginator and received by the recipient, while the second communicationpath carries signals transmitted by the recipient and received by theoriginator.

When the telephone call recipient attempts to place a three-way call bydepressing his switch hook as described above, the recipient's endoffice switch receives a first pulse which it transmits via the publicswitched telephone network along a one-way, digital communication pathto the originator's telephone. After receiving the first pulse (known,in the telecommunications industry, as a switch hook request), therecipient's end office switch transmits a first period of "silence"lasting approximately 250 milliseconds to 1.2 seconds followed by asecond pulse created when the recipient releases his switch hook. Incombination, the first pulse, first period of silence, and second pulseare known in the telecommunicatons industry as a "hook-flash event".Similar to the first pulse, the first period of silence and second pulseare received at the originator's telephone via the one-way, digitalcommunication path of the public switched network. In response to thedepression and release of the recipient's switch hook, the recipient'send office switch suspends the telephone call and outputs a dial tone tothe recipient. While the recipient dials the third party's telephonenumber, a second period of "silence", lasting at least 4 seconds, isobservable at the originator's telephone.

While the detection of an attempted three-way call placement is of,perhaps, minor importance in many environments, the detection andresponse to an attempted placement of a three-way call is extremelyimportant in the penal environment. Since prisoners often have abundantamounts of free time on their hands, inmate telephone privilegesfrequently provide inmates with opportunities for making nuisance callsto judges, victims, and other parties. Fortunately, some of today'stelephone systems can prevent inmates from placing direct calls toparties who are previously identified to the systems by their telephonenumbers. Unfortunately, many of the same telephone systems cannotprevent inmates from placing a call to a cohort "on the outside" havingthree-way calling service who, in turn, connects the inmate with thethird party with whom the inmate wishes to talk.

U.S. Pat. No. 5,319,702, Kitchin et al., represents one system which hasattempted to provide an apparatus and method for detecting the attemptedplacement of a three-way call by detecting a hook-flash event.Unfortunately, the apparatus is a premises-based solution and must bephysically integrated with each telephone in order to function properly.As a result, the apparatus is not readily adaptable for use in atelecommunications network which would enable a single apparatus toservice a plurality of telephones and a plurality of premises. Inaddition, the method attempts to detect a hook-flash event, in part, byidentifying a pulse, present in a particular frequency band, andspecific event(s) occuring after the pulse. Because the pulse may bemasked by (or duplicated by) noise created along a communication path orby noise created by an individual seeking to avoid detection and becausethe pulse may occur within a different frequency band, the method wouldappear to suffer from poor reliability and would appear to have a highrate of failing to detect (or erroneously detecting) an attemptedthree-way call placement.

There is, therefore, a need in the industry for an apparatus and methodwhich can more reliably detect and respond to the attempted placement ofa three-way call and can solve other related and unrelated problems thatbecome apparent upon reading and understanding this specification.

SUMMARY OF THE INVENTION

Briefly described, the present invention includes a three-way calldetection and response system which enables, at a location distant fromthe location of the originator's telephone, the detection of andresponse to an attempted three-way call placement by a telephone callrecipient. More particularly, the present invention includes a signalacquisition apparatus which employs a non-intrusive tap to monitor asimplex, digital communication channel (also referred to herein as aone-way, digital communication path) carrying signals from therecipient's end office switch toward the originator's end office switch,and a pattern recognition apparatus and method to detect indicia, on thecommunication channel, which are representative of the attemptedinitiation or placement of a three-way telephone call (also referred toherein as a three-way call signature or, simply, as a signature) by therecipient. The three-way call signature, detected in the presentinvention, includes a first period of silence which precedes a pulse,corresponding to the release of a switch hook (also referred to hereinas a release pulse), which is, in turn, followed by a second period ofsilence. By distinguishing and identifying all three portions of thethree-way call signature, in the above-described sequence and withoutfrequency filtering, from other signals travelling on the digitalcommunication channel, the present invention identifies the attemptedplacement of a three-way telephone call.

In the preferred embodiment of the apparatus of the present invention, abridge repeater (i.e., a non-intrusive tap) is electrically interposedbetween a one-way digital communication path, having multiple channelsand extending between telephone switches, and an interface at a locationbetween the telephone switches. The interface receives an amplified andretimed DS-1 signal from the bridge repeater, demultiplexes the DS-1signal, and ports a pulse code modulated (PCM) signal, corresponding toa selected channel of the DS-1 signal, to a connected digital signalprocessor. A local controller is electrically connected between theinterface, the digital signal processor, and a remote controller by aplurality of control links. The local controller interprets commandsreceived from the remote controller and exchanges various controlsignals via the control links to the interface and the digital signalprocessor. The local controller also transmits various control signalsto the remote controller via a control link, for instance, to signaldetection of a three-way call signature and, hence, an attemptedthree-way call placement. The remote controller is additionallyelectrically connected by a control link to a telephone switch to enablethe remote controller to exercise control over the connection,disconnection, routing, and identification of communication paths. Aplurality of software programs, executed by the remote controller,access a plurality of data tables and, in conjunction, allow the remotecontroller to determine necessary actions and responses by the system.

In accordance with a preferred embodiment of the method of the presentinvention, the three-way call detection and response system receivesnotification of the placement of a telephone call from an originator atan originator telephone, initiates monitoring of the call, and issuescommands causing the completion of the call to a recipient at arecipient telephone. The system monitors and examines digital signalscarried on a communication path from the recipient's end office switchto the originator's end office switch by non-intrusively tapping thecommunication path to acquire duplicate signals, thereby enablingmonitoring without degradation of the signals traveling on thecommunication path. The system continually monitors the digital signalsto detect an attempted three-way call placement which it initiallyidentifies as a "suspected three-way call signature". By subsequentlyanalyzing the signals corresponding to the suspected three-way callsignature, the system determines whether or not the suspected three-waycall signature is an actual three-way call signature and, hence, whetheror not an attempted three-way call placement has been performed by therecipient. Upon determining that an actual three-way call signature hasbeen detected, the system responds, for example, by commandingdisconnection of the telephone call, playing back a recording to theoriginator and recipient telephones, and creating a record of the eventin a data table for later use by administrators.

The three-way call detection and response system, in accordance with thepreferred method, identifies a suspected three-way call signature upondetection of a suspected first period of silence. After receivingadditional digital signals following the suspected first period ofsilence, the system then examines the signals to detect the presence ofa suspected release pulse and a suspected second period of silence, inseries, succeeding the suspected first period of silence. The suspectedfirst and second periods of silence are identified as being actual firstand second periods of silence belonging to an actual three-way callsignature by determining that the suspected periods of silence havesufficient time duration and minimal signal amplitudes. The suspectedrelease pulse is identified as being an actual release pulse belongingto an actual three-way call signature by comparing the spectralcharacteristics (including, but not limited to the combination of timeduration, frequency, and energy level) of the suspected release pulse tothe spectral characteristics of a plurality of known, reference releasepulses using digital pattern recognition techniques. In accordance withthe preferred method, the spectral characteristics of the known,reference release pulses have been previously determined and stored bythe system. Use of the pattern recognition process with a plurality ofreference release pulses, acquired from a plurality of previously madethree-way telephone calls from a plurality of recipient telephones atdifferent locations around the country, enables the system to moreaccurately determine whether or not a suspected release pulse of asuspected three-way call signature is an actual release pulse of anactual three-way call signature and, hence, whether or not a three-waycall placement has been attempted by a telephone call recipient.

Accordingly, an object of the present invention is to detect anattempted three-way call placement using an apparatus located distantfrom an originator telephone.

Another object of the present invention is to detect an attemptedthree-way call placement by monitoring a digital communication pathbetween an originator end office switch and a recipient end officeswitch.

Still another object of the present invention is to detect an attemptedthree-way call placement by monitoring digital signals carried by acommunication path from a recipient end office switch to an originatorend office switch.

Still another object of the present invention is to detect an attemptedthree-way call placement by monitoring signals carried by acommunication path between an originator end office switch and recipientend office switch without degrading the signals.

Still another object of the present invention is to detect an attemptedthree-way call placement using an apparatus positioned electricallybetween telephone switches.

Still another object of the present invention is to detect an attemptedthree-way call placement by detecting a three-way call signaturetransmitted by a recipient end office switch.

Still another object of the present invention is to detect an attemptedthree-way call placement by identifying a first period of silence, arelease pulse, and a second period of silence in series.

Still another object of the present invention is to identify a suspectedrelease pulse as an actual release pulse of an actual three-way callsignature by comparing the spectral characteristics of the suspectedrelease pulse to the spectral characteristics of a plurality of known,reference release pulses.

Still another object of the present invention is to collect and storethe spectral characteristics of a plurality of release pulses of actualthree-way call signatures transmitted by recipient end office switchesat different locations around the country.

Still another object of the present invention is to detect an attemptedthree-way call placement without requiring the physical presence of aspecial detection apparatus at the originator's location.

Still another object of the present invention is to detect attemptedthree-way call placements on a plurality of communication paths withoutrequiring the presence of special detection apparatus at each originatorlocation.

Still another object of the present invention is to improve three-waycall detection accuracy by accounting for the effects of older telephonefacilities, poor connections, and line loss due to the distance betweenthe originator and recipient end office switches.

Still another object of the present invention is to increase thereliability and accuracy of three-way call detection.

Still another object of the present invention is to accurately detect anattempted three-way call placement when noise on a communication pathwould otherwise render difficult, if not impossible, the detection of ahook-flash event.

Other objects, features, and advantages of the present invention willbecome apparent upon reading and understanding the present specificationwhen taken in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram representation of the physical domain of athree-way call detection and response system in accordance with apreferred embodiment of the present invention.

FIG. 2 is a block diagram representation of a three-way call detector ofthe three-way call detection and response system of FIG. 1.

FIG. 3 is a block diagram representation of a remote controller of thethree-way call detection and response system of FIG. 1.

FIG. 4 is a block diagram representation of a program domain of thethree-way call detection and response system of FIG. 1.

FIG. 5 is a flow chart representation of a method for collecting andstoring spectral characteristics of known, reference release pulses inaccordance with a preferred method of the present invention.

FIG. 6 is a flow chart representation of a method for detecting andresponding to a three-way call signature in accordance with thepreferred method of the present invention.

FIG. 7 is a flow chart representation of a method for detecting indiciarepresentative of a three-way call signature in accordance with thepreferred method of the present invention.

FIG. 8 is a flow chart representation of a method for identifying arelease pulse of an actual three-way call signature in accordance withthe preferred method of the present invention.

FIG. 9 is a graphical representation of a three-way call signature inaccordance with the preferred method of the present invention.

FIG. 10 is a schematic representation of a memory having storagelocations for a plurality of state status values in accordance with thepreferred method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in greater detail to the drawings, in which like numeralsrepresent like components throughout the several views, FIG. 1 displaysa block diagram representation of the physical domain of a three-waycall detection and response system 10 and associated components, inaccordance with the preferred embodiment of the present invention. Inthe physical domain, the three-way call detection and response system10, an originator telephone 12 and a recipient telephone 14 connect tothe public switched network (PSN) 16. The originator telephone 12 islocated at a first location (or premises) 18 and connects to a nearbyoriginator end office 20 and, hence, the PSN 16 via analog distributionfacilities 22. The analog distribution facilities 22 carry analogsignals representing a human voice or other sounds between theoriginator telephone 12 and the originator end office 20. Typically, theanalog distribution facilities 22 include two-wire loop start circuits.The recipient telephone 14 is located at a second location (or premises)24, distant from the first location 18, and connects to a nearbyrecipient office 26 and, hence, the PSN 16 via analog distributionfacilities 28. The analog distribution facilities 28 carry analogsignals representing a human voice or other sounds between the recipienttelephone 14 and the recipient end office 26. Typically, the analogdistribution facilities 28 include two-wire loop start circuits.

Although illustrated by a single symbol, the originator telephone 12represents a plurality of telephones available to one or more users at afirst location 18 (or at multiple first locations 18). Similarly, therecipient telephone 14 represents a plurality of telephones available toone or more users at a second location 24 (or at multiple secondlocations 24). Also, the originator and recipient telephones 12,14represent any of a large variety of currently known telephone stations,including, but not limited to, rotary, Dual Tone Multi-Frequency (DTMF),private telephone stations, smart telephone stations, and Private BranchExchange (PBX) stations. In addition, the originator and recipient endoffices 20,26 form an end office pair which is representative ofmultiple originator and recipient end office pairs, each of which, inpart, telephonically links an originator telephone 12 at a firstlocation 18 and a recipient telephone 14 at a second location 24. Eachoriginator and recipient end office 20,26 also, preferably, includes acodec device 21,27 interposed between the respective analog distributionfacilities 22,28 and a respective end office switch 23,29. The codecdevices 21,27 are bi-directional devices which convert the analogsignals carried by the analog distribution facilities 22,28 into pulsecode modulated (PCM) digital signals used by the end office switches23,29 and vice versa.

In accordance with the preferred embodiment as seen in FIG. 1, acommunication path 30 extends between the originator end office 20 andthe recipient end office 26 to carry the voice and sound energy of atelephone call between the originator telephone 12 and the recipienttelephone 14. The communication path 30 is, preferably, a conventionalT1facility carrying digital signals and includes two, one-way, digitalcommunication paths 30a,30b extending between the originator end office20 and the recipient end office 26 and passing through inter-exchangecarrier switches 32,34. As denoted by the arrows, the firstcommunication path 30a carries signals transmitted from the originator'send office switch 23 toward the recipient's end office switch 29, whilethe second communication path 30b carries signals transmitted from therecipient's end office switch 29 toward the originator's end officeswitch 23. It is understood that the communication path 30 representsmultiple PCM communication paths (also referred to herein as channels)connecting pairs of originator and recipient telephones 12,14 (and pairsof originator and recipient end office switches 23,29) and carryingdigital signals in a multiplexed DS1 format. It is also understood thatall methods through which signals travel between the originator andrecipient end office switches 23,29 are considered covered by the scopeof the present invention. It is further understood that the PSN 16includes a great variety of interconnecting switches, including otherend office switches (also known as local exchange carrier central office(LEC CO) switches), access tandem switches, and long distance carrierpoints of presence switches and that the communcation path 30 may berouted through many such switches in order to couple the originator endoffice switch 23 and the recipient end office switch 29. LEC's areunderstood to include, but are not limited to, Regional Bell OperatingCompanies (RBOC's) and the Independent Telephone Companies (ITC's).

The three-way call detection and response system 10, as displayed inFIG. 1, is located outside the PSN 16 at a position distant from theoriginator and recipient end office switches 23,29 and, preferably,includes a conventional telephony switch 36 through which communicationpath 30 is also routed. One example, but without limitation, of anacceptable switch 36 is a Model SDS-1000 available from Summa Four, Inc.of Manchester, N.H. In an alternate embodiment, the switch 36 is a Model20/20 available from Harris Corporation of Melbourne, Fla. The switch 36enables special handling of telephone calls which are routed through theswitch 36 by the inter-exchange carrier switches 32,34 based in partupon the telephone number assigned to the originator telephone 12. Forinstance, a telephone call made from a telephone number assigned to anoriginator telephone 12 located at a prison (i.e., a first location 18)may be routed through switch 36 to enable special handling of thetelephone call including, but not limited to, termination (ordisconnection) of the telephone call, playback of a recording to thecall's originator and recipient, and operator intervention. Thethree-way call detection and response system 10 further includes aremote controller 38 which electrically connects to the switch 36 via acontrol line 40. Preferably, signals are carried by control line 40 inan ethernet protocol. In an alternate embodiment of the presentinvention, the remote controller 38 connects to a switch of the PSN 16located between end office switches 23,29, thereby eliminating switch36. The remote controller 38 executes a number of software applications,as described below, which cause the remote controller 38 to send variouscommands (i.e., control signals) to switch 36 (or, in alternateembodiments, to a switch of the PSN 16) which control, at least, theconnection, disconnection, and routing of telephone calls through switch36 (or, in the alternate embodiments, control a switch of the PSN 16).

In accordance with the preferred embodiment, the three-way calldetection and response system 10 also includes a bridge repeater 42which connects electrically, in a non-intrusive manner, to communicationpath 30b via signal line 44 at a location 46 between switch 36 andinter-exchange carrier switch 34 and, hence, distant from the locations18,24 of the originator and recipient telephones 12,14. The bridgerepeater 42 functions as a conventional bridge repeater and taps signalsfrom communication path 30b without substantial degradation of thedigital signals carried by communication path 30b. One example, withoutlimitation, of an acceptable bridge repeater 42 is a Larus 1109available from Larus Corporation and is capable of handling at least 24PCM channels. It is understood that other apparatus and methods ofnon-intrusively acquiring digital signals from communication path 30bare within the scope of the present invention. Communication path 30band, hence, signal line 44 carry multiple PCM channels of digital voiceand sound energy multiplexed in a DS1 format and the bridge repeater 42amplifies and retimes the digital signals transported by each channel.The three-way call detection and response system 10 further includes, asseen in FIG. 1, a three-way call detector 48 interposed electricallybetween the bridge repeater 42 and the remote controller 38. Thethree-way call detector 48 connects electrically to the bridge repeater42 via a signal line 50 and to the remote controller 38 via a controlline 52. Signal line 50, similar to signal line 44, carries multiple PCMchannels of digital voice and sound energy multiplexed in a DS1 format.Control line 52 carries control signals bi-directionally between thethree-way call detector 48 and the remote controller 38 using,preferably, an ethernet protocol. It is understood that the scope of thepresent invention includes other methods of connecting the three-waycall detector 48 to the PSN 16 to acquire digital signals carried bycommunication path 30b.

FIG. 2 displays a block diagram representation of the three-way calldetector 48 in accordance with the preferred embodiment of the presentinvention. Preferably, the three-way call detector 48 includes aninterface 54, a digital signal processor 56, and a local controller 58.The interface 54 is electrically interposed between the bridge repeater42 and the digital signal processor 56 and connects electrically to thebridge repeater 42 via signal line 50. The interface 54, having multipleoutput ports, functions, as readily understood by one skilled in theart, to demultiplex the DS1 channels 30 (or as also referred to herein,communication paths 30) present on signal line 50 and to make eachchannel's digital signals available in PCM format at an output port forselection and routing on signal line 60 to the digital signal processor56. One example, without limitation, of an acceptable interface 54 is aT1 interface card available from Brite Corporation of Wichita, Kans.Control line 62 electrically connects the interface 54 and the localcontroller 58 to enable the bi-directional transfer of control signalsbetween the interface 54 and the local controller 58. Preferably, thecontrol line 62 carries control signals in RS-232 protocol. Anacceptable alternative protocol is the ethernet TCP/IP protocol.Similarly, control line 64 electrically connects the digital signalprocessor 56 and the local controller 58 to enable the bi-directionaltransfer of control signals between the digital signal processor 56 andthe local controller 58. Preferably, the control line 64, similar tocontrol line 62, carries control signals in RS-232 protocol. Anacceptable alternative protocol is the ethernet TCP/IP protocol. Thedigital signal processor 56 includes an internal memory 57 and, asdiscussed below, stores previously collected spectral characteristics ofa plurality of known pulses of three-way call signatures. The localcontroller 58 electrically connects to the remote controller 38 viacontrol line 52 for bi-directional transfer of control signals betweenthe local controller 58 and the remote controller 38. Such controlsignals include incoming commands received and interpreted by the localcontroller 58 and outgoing signals announcing the detection of anattempted three-way call placement to the remote controller 38. Oneexample, without limitation, of an acceptable local controller 58 is aPS-01-0000 central processing unit (CPU) available from BriteCorporation of Wichita, Kans. It is understood that the interface 54,digital signal processor 56, and local controller 58 are representativeof multiple interfaces 54, digital signal processors 56, and localcontrollers 58 which may be utilized in the three-way call detection andresponse system 10.

The local controller 58 receives textual commands from the remotecontroller 38 to control the operation of the interface 54 and digitalsignal processor 56. Upon interpreting the received commands, the localcontroller 58 generates the appropriate control signals necessary tocarry out the commands and transmits the control signals to theinterface 54 and digital signal processor 56 via control lines 62,64,respectively. Typical commands include, at least, commands which causereinitialization of the interface 54 and digital signal processor 56,selection of an interface port for direction of a channel's PCM digitalsignal to the digital signal processor 56, and initiation of three-waycall detection by the digital signal processor 56. Once an interfaceport and, hence, a communication path 30b is selected for monitoring, asdiscussed below, the digital signal processor 56 discretely samples thedigital signals, carried by communication path 30b from the recipient'send office 26 to the originator's end office 20, to detect the existenceof three-way call signature indicia potentially present in the digitalPCM signal. Upon detecting indicia representative of a three-way callsignature (and, hence, an attempted three-way call placement), thedigital signal processor 56 generates a control signal which it sends tothe local controller 58 on control line 64. In response, the localcontroller 58 generates and sends a control signal to the remotecontroller 38 along control line 52 to inform the remote controller 38that an attempted three-way call placement has been detected on aselected interface port and communication path 30b. One example, withoutlimitation, of an acceptable three-way call detector 48 is manufacturedby Brite Corporation of Wichita, Kans.

FIG. 3 displays a block diagram representation of the remote controller38 of FIG. 1. In accordance with the preferred embodiment, the remotecontroller 38 is a fault tolerant, general purpose controller which isappropriately programmed (see below) and which offers utility gradeservice from a redundant architecture which is capable of processingmany applications simultaneously. One example, without limitation, of anacceptable remote controller 38 is a Stratus® XA2000 Model 30 fromStratus Computer, Inc. of Marlboro, Mass. As seen in FIG. 3, two buses,A & B, are both electrically connected to redundant, mirror-imagehardware components, including I/O processors 68a,68b, memory subsystems70a,70b, and CPU subsystems 72a,72b. I/O processors 68a,68b are bothelectrically connected to communications subsystem 74 and to disksubsystem 76 through disk control subsystem 78. Control lines 40,52electrically connect the communications subsystem 74 to switch 36 andthe three-way call detector 48, respectively. A terminal 80 alsoelectrically connects to communications subsystem 74.

The redundant architecture of the remote controller 38 insurescontinuous application reliability and availability. If one componentfails, its redundant, mirror-image component typically continues so thatthere are normally two components performing the same function at thesame time. Also, each CPU subsystem 72a,72b contains duplicate CPU'swhich process the same data at the same time, thus a total of fourprocessors typically work on the same data at the same time. Logiccomparators continually compare the results of each processor. If theprocessors on a board disagree, that particular board is taken off line,an error signal is generated, and its redundant, mirror-image componentcontinues without any processing degradation.

The operation of each component of the remote controller 38 isrelatively straight forward to one reasonably skilled in the art. CPUsubsystems 72 provide processor functions; memory subsystems 70 provideoperating memory; and I/O processors 68 provide input and outputcapabilities. Disk control subsystem 78 provides control of disksubsystem 76, which stores conventional operating system programming,application programming, and data tables. Control lines 40,52 enablebi-directional communication with switch 36 and three-way call detector48, respectively. Terminal 80 provides human interaction with the remotecontroller 38 through communications subsystem 74.

FIG. 4 is a block diagram representation of the program domain of thethree-way call detection and response system 10 in accordance with thepreferred embodiment of the present invention. In the preferredembodiment, the programming domain represents programming found, inlarge part, on the remote controller 38. Running below a virtualoperating system 82 are a switch server 84 and a three-way call detectserver 86. The switch server 84 and three-way call detect server 86 aremulti-tasking, multi-threading processes which provide programminginterfaces between the remote controller 38 and the switch 36 and theremote controller 38 and the three-way call detector 48, respectively.The three-way call detect server 86 has access, via disk controlsubsystem 78, to a configuration table 90 and an event log table 92present on disk subsystem 76. The configuration table 90 stores dataincluding, at least, the number of interface ports available forthree-way call detection, the type of response to employ upon detectionof an attempted three-way call placement, and recorded messages to beplayed back in conjunction with a response. The event log table 92stores data related to an attempted three-way call placement including,at least, the date and time of the attempt and the telephone numbers ofthe originator telephone 12 and recipient telephone 14. Both the switchserver 84 and the three-way call detect server 86 are connected to acall processing application 88 which has access, via the disk controlsubsystem 78, to a port mapping table 94 residing on the disk subsystem76. The port mapping table 94 stores data including data whichidentifies the ports of interface 54 which are in use at a given time.The call processing application 88 communicates with the switch server84 and the three-way call detect server 86 through interprocesscommunication paths represented in FIG. 4 as connecting lines extendingbetween the servers 84,86 and the call processing application 88.

In accordance with a preferred embodiment of the method of the presentinvention, the three-way call detection and response system 10 storesspectral characteristics (including, but not limited to the combinationof duration time, frequency, and amplitude) of a plurality of releasepulses 106 of sample three-way call signatures 100 (see FIG. 9) createdby the making of sample three-way calls from recipient telephones 14 atdifferent recipient locations 24. The spectral characteristics,collected and stored prior to the actual day to day operation of thethree-way call detection and response system 10, are employed by thedigital signal processor 56 as reference characteristics of knownrelease pulses 106 in a comparison and pattern matching step, asdiscussed below, to identify whether or not a suspected release pulse isactually the release pulse 106 of a suspected three-way call signature100. Use of the plurality of sample release pulses 106 and monitoring ofcommunication path 30b between end office switches 23,29 is necessary toenable more accurate detection of three-way call signatures 100 byallowing the system 10 to account for differences in line lossattributable to older facilities, poor connections, and distancesbetween the originator telephone location 18 and the recipient telephonelocation 24, in addition to noise possibly created by an originatorattempting to mask a three-way call placement.

The preferred embodiment of the invented method, seen in the flow chartrepresentation of FIG. 5, begins at step 200 and moves to step 202 wherethe digital signal processor 56 and other components are initialized forcollection of the spectral characteristics of sample release pulses 106.At step 204, the digital signal processor 56 monitors a telephone call,made to a known recipient location 24, by discretely sampling thedigital signals carried by communication path 30b. Upon release of theswitch hook on the recipient's telephone 14 (i.e., thereby creating aknown three-way call signature 100 including a release pulse 106 as seenin FIG. 9), the digital signal processor 56, at step 206, receives thesignal 102 and, hence, the three-way call signature 100 carried bycommunication path 30b from the recipient end office switch 29 towardthe originator end office switch 23. Advancing to step 208, the digitalsignal processor 56 identifies the release pulse 106 present in thethree-way call signature 100 and, at step 210, analyzes the releasepulse 106 to determine its spectral characteristics. At step 212, thespectral characteristics of the release pulse 106 are stored in thedigital signal processor 56 for use as a reference in the subsequentdetection of release pulses 106 of actual three-way call signatures 100.The method, at step 214, determines whether or not all sample releasepulses 106 have been collected. If yes, the method proceeds to step 216where it stops. If no, the method proceeds to step 204 where it monitorsa telephone call made to a different recipient location 24, therebyenabling the collection and storage of spectral characteristics for aplurality of reference release pulses 106 which are created by recipienttelephones 14 at different recipient locations 24.

FIGS. 6-8 are flow chart representations of steps taken by the three-waycall detection and response system 10 of the preferred embodiment of thepresent invention when executing a three-way call detection process,such as is suitable for many penal environments. Refer to the previousfigures when references are made to components previously discussed.

The three-way call detection and response process, as seen in FIG. 6,starts at step 230 and moves to step 232 where the system 10 isinitialized. After initialization, the system 10 waits for anoriginator, such as an inmate, to use an originator telephone 12 toplace a telephone call to a recipient telephone 14 by dialing the numberassociated with the recipient telephone 14. Upon identification of thetelephone call as one requiring monitoring (i.e., by analysis of theorigination number and dialed destination number by the switches of thepublic switched network 16), switch 36, at step 234, receives thetelephone call which has been routed to switch 36 by the other switchesof the PSN 16 and, using a predefined format to signal the remotecontroller 38 on control line 40, switch 36 notifies the remotecontroller 38 that a call requiring monitoring is present at the switch36. One example, without limitation, of an acceptable format is theFeature Group D protocol which is well-known to those reasonably skilledin the art. Advancing to step 236, the telephone call is assigned (ormapped) to a monitorable port of the three-way call detector 48 asdescribed in the following discussion. The remote controller 38 receivesthe control signal from the switch 36 and passes it to the switch server84 which, in response, requests that the call processing application 88make a port assignment. The call processing application 88 requestsidentification of an available port from the three-way call detectserver 86 which accesses the configuration table 90 to determine whetheror not an interface port is available for use. Upon determining that aport is available, the three-way call detect server 86, via the remotecontroller 38 and control line 52, commands the local controller 58 toinitialize the port for monitoring. The three-way call detect server 86provides port identification data for the available port to the callprocessing application 88 which assigns (or maps) the call to the portand updates the port mapping table 94. The call processing application88 instructs the remote controller 38 to signal the switch 36 viacontrol line 40 to complete the telephone call. Upon completion of thetelephone call and establishment of communication path 30 at step 238,the switch 36 signals the remote controller 38, via control line 40, toinform the switch server 84 that the telephone call has been completed.The switch server 84 passes the call's status on to the call processingapplication 88 which instructs the three-way call detect server 86 tobegin monitoring the call. The three-way call detect server 86 transmitsa command, via control line 52, to the local controller 58 to select theassigned port and to initiate monitoring of the port by the digitalsignal processor 56.

The digital signal processor 56, at step 240, monitors the digitalsignals which are transmitted from the recipient's end office 26 to theoriginator's end office 20 on communication path 30b and which areported to signal line 60 by the bridge repeater 42 and interface 54 todetect indicia representative of an attempted three-way call placement100 (i.e., a three-way call signature 100). The indicia 100 include, asdisplayed in FIG. 9, a first period of silence 104, a release pulse 106,and a second period of silence 108 in series. Preferably, the digitalsignal processor 56 searches, by applying discrete sampling techniqueswell-known in the field of digital signal processing to the digitalsignals 102, for a first period of silence 104 lasting for a duration of240 milliseconds to 1.2 seconds at a signal amplitude below -47 dbm.Similarly, the digital signal processor 56 searches for a second periodof silence 108 lasting, preferably, for a duration of at least 4 secondsat a signal amplitude also below -47 dbm. The digital signal processor56 also searches for a release pulse 106 having, preferably, spectralcharacteristics (including a minimum amplitude of -23 dbm) substantiallysimilar to the spectral characteristics of a known release pulse 106previously collected and stored in the digital signal processor 56 foruse as a reference. The method of operation of the digital signalprocessor 56 is described in more detail below.

Upon determining, by checking the three state statuses 110,112,114(described below) at step 242, that an actual three-way call signature100 (and, hence, an attempted three-way telephone call placement) hasbeen detected, the digital signal processor 56 signals the localcontroller 58 by placing an appropriate control signal on control line64. The local controller 58, in response, places an appropriate controlsignal on control line 52 to inform the remote controller 38 and, hence,the call processing application 88 that an attempted three-way callplacement has been detected by the three-way call detector 48 on aspecified port. The call processing application 88 responds by informingthe three-way call detect server 86 that an attempted three-way callplacement has been detected on the port. The three-way call detectserver 86 accesses the configuration table 90 in order to determine howto handle the detected three-way call attempt. Based upon information inthe configuration table 90, the three-way call detect server 86 respondsto the attempted three-way call placement, at step 246, by performingone or more steps including, but not limited to: (1) notifying switch36, via control line 40, to disconnect the communication path 30 and,hence, the telephone call between the originator's telephone 12 and therecipient's telephone 14; (2) playing a recorded announcement to theoriginator and recipient telephones 12,14; (3) storing a record of theattempted three-way telephone call placement in the event log table 92;(4) performing any combination of the steps of notifying, playing, andstoring described in 1-3 above; and, (5) ignoring the detection of theattempted three-way telephone call placement. It is understood thatother methods of response to the detection of an attempted three-waytelephone call placement are within the scope of the present invention.After responding at step 246, the method stops monitoring the call atstep 248. If no three-way call signature 100 is found at step 242 (i.e.,at least one state status 110,112,114 is false), the method periodicallychecks to see, at step 244, whether or not the call has terminated. Ifno, the method continues monitoring at step 240. If yes, the methodstops monitoring at step 248.

In accordance with the preferred method of the present invention, thedigital signal processor 56, as illustrated in FIGS. 7 and 8, operatesas a state machine defining, preferably, three states (or conditions),corresponding to the indicia representative of an attempted three-waycall placement 100, which must have a true status in order for thesystem 10 to conclude that the recipient has attempted to place athree-way telephone call. A first state, having a status 110 (see FIG.10), represents whether or not an actual first period of silence 104 hasbeen found. For the first state status 110 to be true, the digitalsignal processor 56 must detect the existence of a period of silencemeeting the requirements described above for the first period of silence104. A second state, having a status 112 (see FIG. 10), representswhether or not an actual release pulse 106 has been found. For thesecond state status 112 to be true, the digital signal processor 56 mustdetect the presence of a release pulse, after the first period ofsilence 104, having a minimum amplitude of -23 dbm and spectralcharacteristics substantially similar to the spectral characteristicsof, at least, one of the plurality of reference release pulses 106previously collected and stored in accordance with the preferred method.A third state, having a status 114 (see FIG. 10), represents whether ornot an actual second period of silence 108 has been found. For the thirdstate status 114 to be true, the digital signal processor 56 must detecta period of silence following the pulse 106 and meeting the requirementsdescribed above for the second period of silence 108. If all threestates have a true status 110,112,114, the digital signal processor 56determines that an actual three-way call signature has been found (and,hence, that an attempted three-way call placement has been found)because all of the indicia 100 are present. If all three states do nothave a true status 110,112,114 (i.e., at least one state is false), thedigital signal processor 56 determines that the suspected three-way callsignature is not an actual three-way call signature (and, hence, that anattempted three-way call placement has not occured) because one of theindicia 100 is not present.

The digital signal processor 56, in accordance with the preferred methodand as displayed in FIG. 7, starts a detection process at step 260 andadvances to step 266 where the digital signal processor 56 monitors thedigital signals which are carried by communication path 30b and portedto signal line 60 by sampling and analyzing the digital signals. Thesampling techniques and analysis methods of the digital signal processor56 are considered to be well-known to those reasonably skilled in theart and are, therefore, not discussed herein. The digital signalprocessor 56 monitors the digital signals on communication path 30b forthe existence of a period of silence which it suspects as being thefirst period of silence 104 (see FIG. 9) of a suspected three-way callsignature 100. Upon detecting a suspected first period of silence atstep 266, the digital signal processor 56 determines, at step 268,whether or not the suspected first period of silence meets therequirements set forth above for the first period of silence 104 of anactual three-way call signature. If no, the method retreats to step 266to continue searching for a suspected first period of silence. If yes,the method identifies the period of silence as the first period ofsilence 104 of an actual three-way call signature and, at step 270,defines the first state status 110 to be true. The method continues, atstep 272, where the digital signal processor 56 monitors the digitalsignals on signal line 60, using the steps shown in FIG. 8, for thepresence of a suspected release pulse having a minimum amplitude of -23dbm. To determine, at step 274, whether or not the suspect release pulseis an actual release pulse 106 indicative of an attempted three-way callplacement, the digital signal processor 56 identifies the spectralcharacteristics of the suspected release pulse and compares the spectralcharacteristics to the reference characteristics of known release pulseswhich were previously collected and stored as described above. Detailsof the comparison and pattern recognition method are discussed below. Ifthe spectral characteristics of the suspected release pulse does notsufficiently match the spectral characteristics of one of the pluralityof known release pulses, then the method resets the first state status110 to false at step 276 and loops back to step 266 to begin searchingfor a suspected first period of silence. If, on the other hand, thespectral characteristics of the suspect release pulse sufficiently matchthe spectral characteristics of, at least, one of the plurality of knownrelease pulses, then the digital signal processor 56 identifies thesuspected release pulse as an actual release pulse 106 of an actualthree-way call signature and, at step 278, defines the second statestatus 112 to be true.

Continuing at step 280, in accordance with the preferred method, thedigital signal processor 56 begins monitoring the digital signalspresent on signal line 60 for a period of silence meeting the abovedescribed specifications for a second period of silence 108 of athree-way call signature. At step 282, the digital signal processordetermines whether or not a suspected second period of silence isactually a second period of silence 108 indicative of a three-way callsignature 100. If yes, the digital signal processor 56 identifies thesuspected second period of silence as an actual second period of silence108 and, at step 284, defines the third state status 114 to be true. Themethod then terminates with respect to the monitored telephone call atstep 286. If no, the method, at step 288, resets the first and secondstate statuses 110,112 to be false and returns to step 266 to beginmonitoring for a suspected first period of silence. It is understoodthat the apparatus of the present invention is capable, in effect, ofmonitoring multiple telephone calls simultaneously and that thetermination of monitoring one telephone call does not terminatemonitoring of other telephone calls. Also, it is understood thattermination of the monitored telephone call causes termination ofmonitoring for that call.

FIG. 8 displays the detailed method steps which the system 10 employs,at step 274, to determine whether or not a suspected release pulse isactually the release pulse 106 of a three-way call signature 100. Inaccordance with the preferred method, the process starts at step 300 andproceeds to step 302 where the digital signal processor 56 discretelysamples (using sampling techniques well-known to those reasonablyskilled in the art) the suspected release pulse in order to identify itsspectral characteristics. Then, at step 304, the digital signalprocessor 56 compares the identified spectral characteristics of thesuspected release pulse with the stored spectral characteristics of aknown release pulse 106 collected from one of the plurality ofdifferent, sample recipient telephone locations 24 as discussed above.The digital signal processor 56 utilizes techniques similar to thoseemployed in speech or pattern recognition systems to compare thespectral characteristics of the suspected release pulse and the knownrelease pulse 106. At step 306, the digital signal processor 56determines whether or not the spectral characteristics are substantiallysimilar. If no, then the suspected release pulse is not considered to bean actual release pulse 106 of a three-way call signature 100 and themethod, at step 308, checks to see if the spectral characteristics ofthe suspected release pulse have been compared against all of the storedspectral characteristics for all of the known release pulses 106. If no,the method loops back to step 304 and compares the spectralcharacteristics of the suspected release pulse against the storedspectral characteristics of a different, known, release pulse 106. Ifyes, the method stops at step 312. If, at step 306, a match is foundbetween the spectral characteristics of the suspected release pulse andthe known release pulse 106, the method, at step 310, identifies thesuspected release pulse as an actual release pulse 106 of an actualthree-way call signature 100. The method then stops at step 312.

Whereas this invention has been described in detail with particularreference to its most preferred embodiment, it is understood thatvariations and modifications can be effected within the spirit and scopeof the invention, as described herein before and as defined in theappended claims. The corresponding structures, materials, acts, andequivalents of all means or step plus function elements in the claimsbelow are intended to include any structure, material, or acts forperforming the functions in combination with other claimed elements asspecifically claimed.

We claim:
 1. A method of processing a telephone call, said methodcomprising the steps of:identifying a first location as a locationrequiring monitoring; establishing a communication path to allowmonitoring; mapping the communication path to a port of a monitoringapparatus; monitoring the communication path connecting a telephone calloriginator at the first location and a telephone call recipient at asecond location to detect an attempted three-way telephone callplacement by the telephone call recipient, wherein monitoring isperformed at a location distant from the first location, and upondetection of an attempted three-way telephone call placement, respondingin a predetermined manner.
 2. The method of claim 1, wherein the step ofmonitoring includes, at least, monitoring the communication path todetect indicia representative of a three-way call signature.
 3. Themethod of claim 1, wherein the step of monitoring includes, at least,comparing spectral characteristics of a suspected release pulse of asuspected three-way call signature to spectral characteristics of aknown release pulse of a known three-way call signature to detecttransmission of a three-way call signature on the communication path. 4.The method of claim 1, wherein the step of monitoring includes, atleast, monitoring a communication path directing a plurality of digitalsignals between the telephone call recipient and the telephone calloriginator.
 5. The method of claim 1, wherein the step of monitoringincludes, at least, monitoring a communication path carrying a pluralityof signals traveling only in a single direction from the telephone callrecipient to the telephone call originator.
 6. The method of claim 1,wherein the step of monitoring includes, at least, observing a signaltraveling on the communication path absent interruption of the signal.7. The method of claim 1, wherein the step of monitoring includes, atleast, monitoring a communication path established between a firsttelephone switch and a second telephone switch at a position between thefirst and second telephone switches, wherein the first and secondtelephone switches are located distant from the first location.
 8. Themethod of claim 1, wherein the method further includes, at least,controlling the steps of monitoring and responding with a remotecontroller.
 9. The method of claim 1, wherein the method furtherincludes, at least, controlling the step of monitoring with a localcontroller.
 10. The method of claim 1, wherein the step of monitoringincludes, at least, identifying a communication path to monitor.
 11. Themethod of claim 1, wherein the method further includes, at least,establishing a predetermined response to the detection of an attemptedthird party telephone call.
 12. The method of claim 11 above, whereinthe step of establishing includes, at least, storing the predeterminedresponse.
 13. The method of claim 1, wherein the step of respondingincludes, at least, disconnection of the communication path between thetelephone call originator and the telephone call recipient.
 14. Themethod of claim 1, wherein the step of responding includes, at least,storing a record of the attempted three-way telephone call placement.15. The method of claim 1, wherein the step of responding includes, atleast, playing a pre-recorded announcement to the telephone calloriginator and the telephone call recipient.
 16. The method of claim 1,wherein the step of responding includes, at least, ignoring thedetection of the attempted three-way telephone call placement andallowing the establishment of a communication path to a third party. 17.A method of detecting and responding to an attempted three-way telephonecall placement, the method comprising the steps of;acquiring a digitalsignal from a communication path; and examining the digital signal todetect a signature representative of attempted three-way telephone callplacement; wherein the step of acquiring includes, at least, tapping thecommunication path without substantially degrading the digital signaltransmitted on the communication path.
 18. The method of claim 17,wherein the step of acquiring includes, at least, amplifying theacquired digital signal.
 19. The method of claim 18, wherein the step ofexamining includes, at least, sampling the digital signal to detect athree-way call signature comprising at least a first period of silence,a release pulse, and a second period of silence occuring sequentially.20. The method of claim 19, wherein the step of sampling includes, atleast, detecting a first period of silence lasting for a period of timeranging between 250 milliseconds and 1.2 seconds.
 21. The method ofclaim 19, wherein the step of sampling includes, at least, detecting asecond period of silence lasting for a period of time measuring at least4 seconds.
 22. The method of claim 17, wherein the step of examiningincludes, at least, sampling the acquired digital signal to detect arelease pulse.
 23. The method of claim 22, wherein the method furtherincludes, at least, identifying a plurality of spectral characteristicsof each of a plurality of previously identified release pulses.
 24. Themethod of claim 23, wherein the step of examining further includes, atleast,sampling the digital signal to identify a suspect release pulse,determining a plurality of spectral characteristics of the suspectrelease pulse, comparing the plurality of spectral characteristics ofthe suspect release pulse to each identified plurality of spectralcharacteristics of previously identified release pulses to discover amatch between pluralities of spectral characteristics, and upondiscovering a match between pluralities of spectral characteristics,identifying the suspect release pulse as the previously identifiedrelease pulse having the plurality of spectral characteristics whichmatches the plurality of spectral characteristics of the suspect releasepulse.
 25. An apparatus for processing a telephone call, said apparatuscomprising:a three-way call detector, connected to a communication pathat a location distant from an originator telephone, wherein saidcommunication path connects said originator telephone and a recipienttelephone; a controller operably connected to said three-way detector,and a bridge repeater electrically interposed between said three-waycall detector and said communication path.
 26. The apparatus of claim25, wherein,said communication path carries digital signalsrepresentative of audible sound and voice energy, and said three-waycall detector analyzes digital signals acquired from said communicationpath.
 27. The apparatus of claim 25, wherein said communication pathcarries signals transmitted by said recipient telephone and received bysaid originator telephone.
 28. The apparatus of claim 25, wherein saidthree-way call detector connects to said communication path at alocation between a first switch and a second switch.
 29. The apparatusof claim 25, wherein said controller connects to a switch positionedelectrically between said originator telephone and said recipienttelephone.
 30. The apparatus of claim 25 wherein,said communication pathcarries indicia representative of a three-way call signature created atthe recipient telephone, and said three-way call detector receives saidindicia, whereby said three-way call detector analyzes said indicia todetect an attempted three-way call placement.
 31. The apparatus of claim25, wherein said three-way call detector includes, at least, a digitalsignal processor.
 32. A method of detecting and responding to anattempted three-way telephone call placement, said method comprising thesteps of;acquiring a signal by monitoring a communication path from amonitoring device connected in parallel to the communication path; andexamining the signal to detect a signature representative of attemptedthree-way telephone call placement, and responding in a predeterminedmanner.
 33. An apparatus for processing a telephone call, said apparatuscomprising:a three-way call detector connected in parallel to acommunication path at a location distant from a first telephone, whereinsaid communication path connects said first telephone and a secondtelephone; and a controller operably connected to said three-way calldetector.